No, at WDW Fantasyland is not tight, they have TONS of rom.....At DL, parts of Fantasyland is tight, but still not bad.
I think it might be time for a major overhaul of both Fantasylands though, basically moving everything around (or a lot of it) and rebuilding all of the rides and entrances, bringing them up to modern technology, while maintaing the escence of the rides, don't go messing them up, but when I say modern technology, I mean things like this where vehicles can be pulled off to load and unload. If they could do it with Space Mountain at
Disneyland, I do not see why it couldn't be done with Peter Pan.
What I would do is similar to space mountain, when the vehicle reaches the Wheel Chair loading area, the vehicle and track slides over to the side, while there is an empty piece of track that slides into the place of the track that was just removed. In addition what it does when it comes back is they have an empty vehicle and that vehicle slides out, while the wheelchair vehicle slides in, so there is no wait for the "empty location," as when they come back the empty vehicle gets put back into service.
This eliminates the problem of the vehicle not getting back on the track properly, it also would reduce the amount of space that is needed to do this, all you would need to do is move the FP machines to a new location (perhaps inside the gift shop and find a new home for the gift shop). It really wouldn't take that much to do it either, probably about a month downtime at most, and since this method could be used to provide an unlimited amount of time to load, as the ride would continue to operate while loading, there would be no problems with making it a vehicle that a person in a wheelchair could remain in thier chair.